Real number on gawk

Question

I am using gawk on a windows computer with cygwin. What i am trying to do is find min and max from three columns, two are lat and lon and the third column is the value.

This is the code:

echo off    
for /f "tokens=1,2,3 delims= " %%a in    
  ('gawk "BEGIN {maxc = 0} {maxlo=0} {maxla=0}    
   {if ($3>maxc) maxc=$3} {if ($1>maxlo) maxlo=$1} {if ($2>maxla) maxla=$2} END    
   {print maxc, maxlo, maxla}" %file%.projected')    
do (
  set maxc=%%a    
  set maxlo=%%b    
  set maxla=%%c    
)
echo max is %maxc%
echo max is %maxla%
echo max is %maxlo%

for /f "tokens=1,2,3 delims= " %%a in    
 ('gawk "BEGIN {minc =1000} {minlo=1000} {minla=1000}    
  {if ($3<minc) minc=$3} {if ($1<minlo) minlo=$1} {if ($2<minla) minla=$2} END    
  {print minc, minlo, minla}" %file%.projected')    
do (
  set minc=%%a    
  set minlo=%%b    
  set minla=%%c    
)    
echo min %minc%    
echo min %minla%    
echo min %minlo%    

What i get is:

max is 465.053890    
max latitude is 31.846428    
max is 34.877658    
min 19.976970    
min 31.846428    
min 34.877658    

The min and max are the same for the lon and lat. How can i compare real numbers?

Answer 1

I'm reasonably sure that this line

'gawk "BEGIN {minc =1000} {minlo=1000} {minla=1000}

doesn't do what you think it does. (Frankly, I'm astounded it compiled at all, I don't think it would have in Kernighan AWK.) And a lot of what's going on here is actually in, what, a Window BAT file?

But here are some guesses.

• I think the line I quoted above sets minc at start time, and then sets minlo and minla every time it reads a line. Better would be

.

 'BEGIN { minc = 1000; minlo = 1000; minla = 1000; } ....

or even

 'BEGIN { minc = minlo = minla = 1000; } ....

• in AWK you have to watch out a little with comparisons, because if you aren't careful it coerces your numbers to string and does a string compare (ie lexicographic ordering) instead of a numeric compare.

Ack, tried to do this as an answer to a comment. No go.

The reason the first line doesn't work is that AWK lines have the form

PATTERN { code }

where PATTERN is some expression that identifies a set of input records (usually lines) on which the code part operates. There are some special cases, for example BEGIN, which "matches" before the first time is read. Another special case is the empty pattern, which matches every line. So what you had was being interpreted as

BEGIN {minc  =1000}
      {minlo =1000}
      {minla =1000}

So, before the first line of input is processed, minc is set to 1000. Following that, on every input line, minlo and minla are set to 1000. My versions, since they all do the initialization in a BEGIN line, just initialize the values once.